Manufacture of lubricating oil



Jan 16, 1951 T. J. WALSH ETAL MANUFACTURE oF LUBRICATING oIL Filed De'c.3, 1946 Patented Jan. 16, 1951 2,538,066 MANUFACTURE 0F LUBRICATING OILThomas J. Walsh,

Shaker Heights, Godfrey L. Ladd, Toledo, and Donald W.

Heil, Cleveland,

Ohio, assignors `to The Standard Oil Company,

Cleveland, Ohio, a corporation .of Ohio Application December 3, 1946,Serial No. 713,710

The present invention relates to the manufac ture of lubricating oil andmore particularly to new and improved methods for refining petroleumlubricating distillates to produce lubricating oils of high quality.

Petroleum lubricating distillates are fractions having a relatively wideboiling range and as usually fractionated contain some gas oil, variouslubricating oils or blending stocks and wax. 'Close fractionation mightbe employed to separate the gas oil fromthe lubricating oils and wax,but some of the lubricating fractions and waxes distill in the samerange and must be separated from each other by methods other thandistillation. Since the presence `of gas oil helps inthe separation ofthe wax from the lubricating oil, it is the usual practice tofractionate the lubricating distillate with some gas oil in it.

The lubricating oils or blending stocks in the fraction are separableinto cuts including the light or pale oils which are relativelylnon-viscous and the heavier or viscous machinery oils. Theselubricating oils or blending `stocks may be used `as such or blended togive a lubricating oil of 'conventional viscosity.

In refining petroleum lubricating distillates, :it has been customary,heretofore, first to re- :move the wax from the fraction such as bychilling and filtering, and then to fractionate the dewaxed oil atatmospheric pressure to remove the gas oil and to form lubricating oilblending-stocks of various viscosities, a practice known as rerunning.The fractions thus separated by the re- `running, comprising a group oflubricating blending stocks, are then separately treated with c.

sulphuric acid to iremove undesirable components in lubricating oil.Following .the acid treatment, each acid-treated oil stock is separatelyneutralized, e. g., with an `alkaline material or preferably bycontacting with clay.

The method outlined brieiy above is disadvantageous in several `materialrespects. In ithe rst place, it necessitates a large amount of tankageor equipment for acid and/0r lclay treating the several lubricating oilblending stocks produced in the rerunning operation. Also, we have foundthat itproduces only a small yield of heavy neutral oils because of the.loss in viscosity yresulting .from the separate treatment of theseveral stocks. Further, clay contacting the stocks as a `final stagegives the Vproduct a somewhat objectionable odor. The :slack wax fromthe lpressing `operation alsohas a poorcolor. resulting Vin a moredimcult sweat 1 lClaim. (Cl. IE6-19) 'v make the products unmarlietable.

step without any cracking are of ing operation and subsequent loss inyield of crude vscale wax.

In an effort to overcome the deficiencies of the method described above,it has been proposed to treat the lubricating stock with acid. and/orclay and then rerun the treated stock in the usual manner to separatethe several lubricating oil blending stock fractions. However, it wasfound that with this method of operation `there appears to be somecracking of the heavier fractions, resulting in the production oflighter materials as well as olenic and unstable compounds whichadversely affect the color and odor of the blending stocks produced tosuchan extent as to This method has not found favor in commercialoperations. In fact, the art has been careful to avoid operationswherein the rerunning vstep is the last or final treating and separationstep.

The objects achieved in accordance with the invention include theprovision of an advantageous method of refining and separatingwaxcontaining lubricating distillates whereby lubricating oil blendinglstocks or fractions are separated after the entire fraction, before orafter dewaxing, has been acid rened; the provision of a method ofseparating lubricating oil fractions directly from dewaxed and acidvrefined lubricating distillate by distillation under a reducedpressure; and other objects which will become apparent as details andembodiments of the invention are set forth hereinafter.

In accordance with our invention, we propose to rerun the lubricatingdistillate fraction under reduced pressure after carrying out thetreating operation with sulphuric acid and/or clay. In this way, it ispossible to distill olf the several lubricating oil blending stockfractions as a final of the heavier fractions and without adverselyaffecting the odor and color of the lubricating oil stocks obtained.

By virtue of this novel procedure only a minimum amount of tankageequipment is required for the acid treating operations since the entireoil fraction, either with or without the Wax therein, is treated as aunit instead `of treating Vthe several lubricating stocks obtained after,rerunning', as ,in the prior art. This is a vmarked advantage from theequipment cost and upkeep viewpoint. There is also greater ease inseparating and disposing of the acid sludge. Further, the iinishedlubricating oil blending stocks good color and odor andare ready to bepackaged and sold directly or `blended as they come-from athe `rerunningunit. This isdesirablc from the operation viewpoint since it givesbetter control of the viscosity of the final product.

In one embodiment of the invention, we iirst subject the petroleumlubricating distillate to be refined to a dewaxing operation in whichwax is removed from the initial fraction in any conventional manner,such as by chilling and filtering. It may or may not be desirable tohave a solvent present depending on the amount and character of the waxpresent in the initial fraction. The dewaxed oil is then subjected totreatment with sulfuric acid and/or clay and the refined oil is fed tothe rerunning unit where the several lubricating oil blending stocks areseparated as a final step. if gas oil is present as a solvent in theinitial fraction and is separated in the rerunning operation, it may berecycled to the dewaxing plant. y

In another embodiment of the invention, the paraiiin lubricatingfraction is first treated with 'sulphuric acid and/or clay and therefined` fraction is dewaxed in any conventional manner. The dewaxed oilis then rerun to produce the desired lubricating oil blending stocks asa final step. As in the foregoing embodiment, if one vof the rerunfractions comprises gas oil which has been used as a solvent, this maybe recycled to the dewaxing plant prior to the dewaxing operation.

The invention may be better understood from the following detaileddescription taken Vin conjunction with the accompanying` drawings, inwhich:

Figure l a flow sheet of the successive steps followed in a method formanufacturing lubricating oil blending stocks according to theinvention; and

Figure 2 is a iiow sheet of a modified method for producing lubricatingoil blending stocks in accordance with the invention.

The starting materials used in the methods described as illustrative ofthe present invention is a paraffin distillate comprising a crudepetroleum fraction boiling higher than gas oil. It is usually a wide cutand may include a certain amount of gas oil in addition to variouslubricatingoil blending stocks, wax, etc.

In'the embodiment illustrated in Figure 1 of the drawings, thelubricating distillate starting material is first fed to a pressingplant where slack wax is taken ofi by chilling and pressing. In order tofacilitate the pressing operation, it is desirable to have a suitablepetroleum product, such as gas oil, for example, in the fraction. Thismay be contained in the fraction as it is initially separated, or it maybe obtained subsequently from the rerunning operation as described ingreater detail hereinafter. The charge should preferably contain about 5to 35 per cent by volume of gas oil based on the total mixture, and thefraction should be slowly chilled down to about 19 to +20 F.

lThe chilled mixture is then filtered in theusual manner. The slack Waxis taken off and is fed to a sweating plant Where oil is separated fromthe solidified Wax by gradually raising the'temperature of the Wax cakeand allowing the'oil'to drip from the wax crystals in the conventionalmanner. The Foots oil is drained off and collected and used for specialpurposes or added to th'e pressed oil, leaving the crude scale wax whichmay be subsequently refined, if desired.

"if The. entire quantity of pressed oil from the pressing plant is' thenfed tof the acid refining plant where it is irsttreated with sulphuric'acid,

for example, for the purpose of removing undesirable components. Theacid sludge obtained in the treating operation is then separated and therened oil is subsequently treated with a suitable alkaline material,and/or preferably contacted with clay, for the purpose of neutralizingthe acid in the charge. The expression acid relining as used hereinincludes the treatment with acid followed by treatment with an alkalinematerial such as clay, if this is required. The details of the acidtreating operation are known to the art and usually about 1 to 100pounds sulphuric acid is used per barrel of oil, followed byneutralization with approximately 3 to 90 pounds of absorbent clay perbarrel of oil. The clay and the oil are separated by filtration and therefined oil is conducted to a rerunning unit Where the severallubricating oil blending stock fractions are distilled off under vacuumas a final step. Preferably, the rerunning operation is carried outunder a vacuum of less than `E300 mm. Hg., preferably 50 to 150 mm. Hg,absolute pressure.

As indicated above, the lubricating distillate starting material usuallyincludes gas oil as one of its components. In the rerunning operationthe gas oil is one of the fractions distilled olf, and it may be fedback to the pressing plant, thus providing for the dilution of thecharge prior to the pressing operation. If this is done, it will not benecessary to include as much gas oil in the initial fraction, In orderto inject the gas oil into the system, at the start of the process, itcan be added from an outside source or can be included in thelubricating distillate feed for a time sufficient to build up a requiredamount of recycle between the rerunning and pressing operations.

If the gas oil is recycled from the rerunning unit to the pressing plantit is necessarily subjected to repeated treatment with sulphuric acidand/or clay along with the rest of the paraffin distillate charge.Consequently, it continues to use up the acid because retreatmentcontinues t take oli more and more of the gas oil components and reduceit in volume to a total of 5D per cent before becoming a stable whitegas oil capable of being continuously recycled without further lossunder the circumstances, and considering the cost of recyclingequipment, it may be more economical not to recycle gas oil.

The lubricating oil blending stock fractions obtained from the rerunningoperation will include a light oil having a viscosity of about SSUv' atF. and heavier oils of 150, 200 and ranging up to viscosities of 300 oreven 400 SSU at 100 F.

The refining of lubricating oils in accordance with the novelmethodoutlined above hasbeen found to result in a very considerablesimplification of refinery operations with a corresponding reduction oftankage requirements and elimination of lag in processing. Further, thefinished oils are characterized by improved odor and color. Only one,acid treating step is necessary, and this is always the same and isapplied to the same kind vof material as distinguished from thevariations -when the Whole oil is treated in accordance with theinvention, the viscosity of the oil and sludge is lower than wasformerly the case with the heavy oil treating operations, and separationand disposal is easier. It has also been found that less caustic isrequired for neutralizing the acid sludge.

In the alternative embodiment of the process, the lubricating distillatestarting material may rst be treated with sulphuric acid and/or clay andthen subjected to the pressing operation, as shown in greater detail inFigure 2. In addition to the advantages described heretofore, thisalternative embodiment also results in improved color and an increasedyield of the crude scale wax produced from the slack wax obtained fromthe pressing plant because the Wax has been acid treated beforepressing. Further, we have noted an improvement in the pressability oflubricating distillate stocks so that heavier lubricating distillatescan be processed in accordance with the method, resulting in greateryield of viscous oils from the charge.

This modication is especially advantageous Where it is desired torecycle gas oil from the rerunning unit to the pressing unit to dilutethe charge prior to the pressing operation. Since the acid treatingoperation is carried out prior to the pressing operation in themodication illustrated in Figure 2, the recycled gas oil is notsubjected to re-treatment.

In this embodiment, a further saving is obtained if the gas oil in thelubricating distillate is removed (stripped) prior to the sulpnuric acidtreating step. This cuts down the consumption of treating agent andincreases the amount of blending stock which may be produced from aplant of any given size.

While several representative embodiments have been described in detailherein, the invention is not intended to be limited thereto but issusceptible of numerous changes in form and detail within the scope ofthe appended claim.

We claim:

A method of producing lubricating oil blending stocks from a lubricatingdistillate fraction including both the light or pale oils which arerelatively non-viscous and the heavier or viscous machinery oils, whichcomprises dewaxing the oil in the presence of a recycled acid-treatedgas oil, and then acid rening said lubricating distillate fraction inthe presence of about 5 to 35% of said acid-treated gas oil, and thensubjecting the de- Waxed and acid-rened stock to distillation under areduced pressure as a final step to separate it into a plurality ofdewaxed and acid-refined lubricating oil blending stocks andacid-treated gas oil, and recycling said acid-treated gas oil to saiddewaxing step.

THOMAS J. WALSH. GODFREY L. LADD. DONALD W. HEIL.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,327,184 Von Groeling Jan. 6,1920 1,388,832 Cobb Aug. 23, 1921 1,559,981 Petty 1 Nov. 3, 19251,802,942 Govers Apr. 28, 1931 1,947,817 Wallis Feb. 20, 1934 2,057,923Slater Oct. 20, 1936. 2,103,898 Fellows Dec. 28, 1937 2,117,984Richardson et al. May 17, 1938 2,142,359 Lederer et al Jan. 3, 1939

